EMG-controlled neuromuscular stimulation is a rehabilitation technique which allows volitional activation of paretic limbs in patients with stroke. This type of active training has been shown to be more effective than passive exercises. The devices used in these pilot studies, however, relied on surface electrodes for EMG recording and muscle stimulation, resulting in low sensitivity to the EMG activity, limited selectivity of muscles for activation, and pain with stimulation. These factors have hindered the clinical adoption of this as a therapeutic intervention. The purpose of this project is to develop a percutaneous intramuscular sensing-stimulation system which overcomes the deficiencies of the surface electrode system. During the completed Phase I study, a prototype device was developed to extract weak EMG signals from stimulation artifacts, and to activate specific muscles without inducing pain. The preliminary clinical study in patients with chronic hemiplegia has demonstrated the technical feasibility of this intervention. During the proposed Phase II study, a pre-production device will be designed, fabricated, and tested. A randomized controlled pilot clinical study will be conducted in patients with recent hemiplegia due to stroke to demonstrate the effectiveness of EMG-controlled stimulation in improving motor impairments in this patient population. PROPOSED COMMERCIAL APPLICATION: The device developed by this project can be used in the rehabilitation process of many hemiplegic stroke survivors. The training promoted with this device is expected to accelerate recovery, shorten hospitalization period, reduce attendant needs, and thus improve patients' quality of life and lower medical care cost.